The National Comorbidity Survey - Adolescent (NCS-A) is a survey of 10,000 adolescents being carried out in parallel with the National Comorbidity Survey Replication (NCS-R) and National Comorbidity Survey 2 (NCS-2). The goal of NCS-A is to produce nationally representative data on the prevalences and correlates of mental disorders among youth. There is emerging evidence regarding the importance of the association between neuroendocrine hormones and psychiatric disorders, particularly depression and anxiety; some recent research even suggests that certain hormones such as testosterone and the Dehydroepiandrosterone (DHEA)/cortisol ratio may predict the incidence of depression. However, most of the information on associations between neuroendocrine parameters and psychopathology is based on non-systematic small samples; moreover, there is a general lack of population baseline data on neuroendocrine or reproductive hormones in a nationally representative sample of the age group spanning childhood and adulthood. The lack of population baseline data has also precluded proper evaluation of the intriguing sex and developmental differences in the associations between testosterone and depression, cortisol with both anxiety and depression and the DHEA/cortisol ratio with stress reactivity. The NCS-A, a combined probability and school-based multi-ethnic sample of 10,000 U.S. adolescents, provides an excellent opportunity for the collection of this essential baseline information, as well as information on associations between neuroendocrine parameters and the common mental disorders, particularly mood and anxiety disorders. The primary aims of the NCS-A are: o To examine the associations between endocrine measures with anxiety and depression in youth; o To evaluate whether there are differences between hormone levels in youth according to pubertal status; o To assess whether high risk youth without disorders themselves have lower levels of endocrine hormones than those with a history of mood or anxiety disorders; o To examine the influence of gender in moderating the risk and protection conferred by variation in expression of these neuroendocrine measures.